1. Field of the Invention
The present invention relates to an apparatus for detecting a light receiving position used with a leveling instrument and the like.
2. Related Background Art
In the past, as an example of apparatus for detecting a light receiving position used with leveling instruments, an arrangement as shown in FIG. 1 has been proposed. In FIG. 1, one ends of sixteen optical fibers 51-66 are arranged along a straight line to form a light receiving plane, and the other ends of the sixteen optical fibers 51-66 are connected to sixteen light dividing or branching devices 51A-66A, respectively, so that two optical fiber paths extending from each light branching device 51A-66A are provided in such a way that respective ones 51b-54b of two optical fibers branched by the light branching devices 51A, 52A, 53A and 54A are connected to a light receiving element A, respective ones 55b-58b of two optical fibers branched by the light branching devices 55A, 56A, 57A and 58A are connected to a light receiving element B, respective ones 59b-62b of two optical fibers branched by the light branching devices 59A-62A are connected to a light receiving elements C, respective ones 63b-66b of two optical fibers branched by the light branching devices 63A-66A are connected to a light receiving element D, and further the other optical fibers 51a, 55a, 59a, 63a branched by the light branching devices 51A, 55A, 59A, 63A respectively are connected to a light receiving element E, the other optical fibers 52a, 56a, 60a, 64a branched by the light branching devices 52A, 56A, 60A 64A respectively are connected to a light receiving element F, the other optical fibers 53a, 57a, 61a, 65a branched by the light branching devices 53A, 57A, 61A, 65A respectively are connected to a light receiving element G, and the other optical fibers 54a, 58a, 62a, 66a branched by the light branching devices 54A, 58A, 62A, 66A respectively are connected to a light receiving element H. The light receiving elements A-H are connected to a detective circuit 70 which is in turn connected to a CPU 71 to which a display 72 is also connected. The deviation of a measured position (position to be measured) can be measured by arranging the light receiving position detecting apparatus at the measured position, by illuminating beam light from a reference position onto the detecting apparatus, and by measuring a position of the beam light on the detecting apparatus. By the way, when the beam light moving in the light receiving plane at the one ends of the optical fibers 51-66 along the latter is situated in a position corresponding to any one of the optical fibers 51-66, it is possible to detect which optical fiber (among the optical fibers 51-66) relates to the beam light and to indicate the result on the display 72, by detecting the position of the beam light by means of two light receiving elements on the basis of the digital information from the two sets of the light receiving elements A-D and E-H.
That is to say, for example, it is assumed that the beam light is situated at a position corresponding to one end of the optical fiber 53; in this case, although the light receiving element A emits a signal representing the fact that it receives the beam light, since the light receiving element A is connected to four optical fibers 51-54, it is impossible to determine which optical fiber relates to the beam light. Thus, such determination is completed by the aid of an output signal from the other set of light receiving elements E-H. More specifically, it is possible to know the fact that the beam light relates to one end of the optical fiber 53, on the basis of the output signals from the light receiving elements A and G.
In the above-mentioned conventional light receiving position detecting apparatus, there arose a porblem that a position smaller than the pitch between the adjacent two optical fibers could not be detected. Further, there also arose a problems that the arrangement and connection of the optical fibers became complex and the assembly operability was troublesome, since the beam light is received by a plurality of optical fibers.